1. Field of the Invention
The present invention relates to a torque fluctuation absorbing apparatus which is used for absorbing the torque vibration from an input shaft coupled to an engine.
2. Description of the Related Art
It is known that a rotational torque from a vehicle's engine has an undesired range of torque fluctuation due to the cycle-by-cycle vibration associated with combustion of the engine and such torque fluctuation or vibration should be absorbed in a power train of the vehicle. In the event rotational torque having a large torsional fluctuation is directly supplied to a power transmission or gear box, it would be damaged, consequently, the input shaft, such as a crank shaft of the engine, provided with a flywheel which is cooperated with a clutch mechanism having a damper.
For purpose of decreasing the range of the torque fluctuation at low engine speed, the inertia member such as the flywheel is divided into an annular driving plate member and a flywheel member, and the damper is interposed between the driving plate and the flywheel member.
The conventional structures having the divided inertia members and the interposed damper are described in the specifications of U.S. Pat. No. 4,274,524, U.S. Pat. No. 4,739,866 and U.S. Pat No. 5,180,044.
As is apparent from the disclosures of these prior specifications, the conventional damper is composed of coil springs which are deformed by the twist or rotation of the driving plate member relative to the flywheel member, or a combination of coil springs and viscous liquid.
It is desired that the damping action be low when a small range of torque fluctuation is produced at a high engine speed, and that the damping action be high when a large range of torque fluctuation is produced at a low engine speed such as below the engine idling speed. However, the conventional damping mechanisms are insufficient to realize the damping actions as described above.